An amicus brief filed this week unites 20 Republicans with plaintiff couples seeking to strike down gay marriage bans in two states.

According to The New York Times, the most prominent signers of the document are former Senator Alan K. Simpson of Wyoming and former Senator Nancy L. Kassebaum of Kansas.

The group argues in its friend-of-the-court brief in support of plaintiff couples challenging the constitutionality of bans in Utah and Oklahoma that “marriage is strengthened” and “the social stability of the family unit are promoted” by allowing gay couples to marry.

The bans were declared invalid in separate cases but both have been appealed to the 10th Circuit Court of Appeals in Denver, which has scheduled hearings on the cases in April.

The cases could lift prohibitions in five states overseen by the 10th Circuit, including Kansas, Oklahoma, Utah, Colorado and Wyoming. Colorado currently recognizes gay couples with civil unions. New Mexico, which is also under the court's jurisdiction, legalized such unions last year.